Laserfiche WebLink
<br />, <br /> <br />tit <br /> <br />tit <br /> <br />e <br /> <br />Colorado's ISF Program is also expanding downstream into cool and warmwater aquatic <br />habitats. Biologic instream flow recommendations can be difficult to quantifY in low elevation <br />stream reaches because the complex aquatic species assemblages that typically inhabit these reaches <br />often have very divergent streamflow requirements. The task of developing cool and warm water <br />biologic flow recommendations may also be complicated by the social and political issues associated <br />with recommending instream flows that will "preserve tht:" natural environment to a reasonable <br />degree" in areas that may be the subject of significant water development pressures. The R2CROSS <br />methodology may also prove useful in cool and warmwater habitats assuming that the hydraulic <br />criteria, which drive the biologic instream flow recommendations, can be adapted to reflect the <br />streamflow requirements of the aquatic species that inhabit these cool and warmwater water <br />environments. However, more sophisticated models may be required in areas of high water <br />development pressure or when habitats other than riffles need to be modeled. <br /> <br />In 1996, the CWCB assembled an Instream Flow Subcommittee to gather input on the <br />public's desires for the future direction of Colorado's ISF Program. The ISF Subcommittee was <br />comprised of several CWCB Board members, representatives of Colorado's water development and <br />environmental communities, and interested members of the general public. ISF Subcommittee <br />discussions were far-ranging, but one of the most recurrent issues was the public's desire for the <br />CWCB to consider other "in-channel" and "over-bank" indicators of the natural environment when <br />quantifYing a stream's instream flow requirements. <br /> <br />"In-channel", the public suggested that the Board consider (I) quantifYing channel- <br />forming/channel maintenance flows, (2) integrating water quantity with water quality and water <br />temperature parameters, and (3) considering flows for recreation purposes. "Over-bank" , it was <br />suggested that the CWCB take a more holistic, ecosystem management approach by recognizing the <br />importance of appropriating flows to maintain riparian and side-channel habitats that are capable of <br />sustaining avian and mammalian species living along the stream corridor in addition to the various <br />life stages of aquatic species that live within the stream. Recent articles on a few of these issues <br />include Brown (1991) on wilderness area water rights, Hill et al. (1991) on out-of-channel flow <br />requirements, and MacDonnell (1991) on wetlands protection. <br /> <br />In some instances, the CWCB has appropriated instream flow rights based on meeting the <br />needs of cool and warmwater aquatic habitats or to protect other "in-channel" or "over-bank" natural <br />environments. For example, the CWCB's recovery flow filings on the l5-mile reach of the Colorado <br />River and on the Yampa River were based on various biologic studies conducted by United States <br />Fish and Wildlife Service (USFWS) biologists. On Little Dry Creek, located near the Denver <br />metropolitan area, the CWCB and CDOW staffs utilized the Instream Flow Incremental <br />Methodology (IFIM) and Physical Habitat Simulation Model (PHABSIM) to develop an instream <br />flow recommendation to protect the habitat requirements of warmwater fish species like creek chub <br />(Semotilus atromaculatus) and white sucker (Catostomus commersoni). The CWCB also <br />appropriated the entire unappropriated flow of Dcadhorse Creek to preserve the unique hydrologic <br />characteristics and the water-dependent natural environment associated with that drainage. As <br />Colorado's ISF Program expands, biologic flow recommendations based on new methodologies or <br /> <br />2 <br />